What term refers to rearrangement of genes on homologous chromosomes that occurs during crossing over in meiosis and serves as a source of variation?

• A. Locus
• B. Autosomes
• C. Crossing over
• D. Recombination

Answer: (D)

Recombination is the rearrangement of genetic material between homologous chromosomes that occurs during crossing over in meiosis and creates new allele combinations, feeding genetic diversity into offspring. During prophase I, homologous chromosomes pair up and non-sister chromatids exchange DNA segments at sites called chiasmata. The exchanged segments produce chromatids with combinations of alleles different from either parent. For example, with genes at two loci, one carrying A/a and the other B/b, crossing over can produce chromosome segments that link A with b and a with B, rather than the parental AB and ab arrangement. This reshuffling is what recombination describes. Locus is simply a gene’s physical location on a chromosome, autosomes are non-sex chromosomes, and crossing over is the actual exchange event itself; recombination focuses on the resulting new allele combinations that increase variation.